Dispersant additives are used to suspend oil-insoluble resinous oxidation products and particulate contaminants in the bulk oil. Ideally, this minimizes sludge formation, particulate-related wear, viscosity increase, and oxidation-related deposit formation. Dispersants are primarily used in gasoline engine and heavy-duty diesel engine oils. They are also used in natural gas engine oils, aviation piston engine oils, automatic transmission fluids and some types of gear lubricants. A variety of commercial dispersant additives have been available and used. For instance, N-substituted long-chain alkenyl succinimides have been used as ashless dispersants. An alkenylsuccinic acid intermediate is obtained by condensing an olefin polymer, such as polyisobutylene, with maleic anhydride. A basic part of the dispersant additive has then been obtained, e.g., from reacting the intermediate with amine compounds such as polyamines. Other previously used dispersants include high molecular weight esters, e.g., a reaction product of an alkylene glycol and a substituted succinic anhydride. Other known dispersants include Mannich bases obtained from high molecular weight alkylated phenols, such as, e.g., the reaction product of a polyalkylenephenol, polyalkylenepolyamine, and an aldehyde. Oil chemists are continually searching for dispersants that achieve optimum dispersancy and low-temperature performance at low concentrations. The present disclosure addresses the need for improved dispersants for lubricating oils and fluids.
An exemplary embodiment of the disclosure is directed to a novel reaction product and method for making the reaction product. The reaction product is a copolymer product obtained by reacting together i) an acylated alkylacrylate copolymer having a number average molecular weight ranging from about 5,000 to about 500,000; ii) a hydrocarbyl acylating agent having a number average molecular weight ranging from about 500 to about 5000; and iii) a compound selected from the group consisting of (a) a polyamine; (b) a polyol; and (c) an aminoalcohol to provide a functionalized polyalkylacrylate copolymer. In several embodiments the mole ratio of (i):(ii) ranges from about 1:10 to about 5:1. An example of a suitable range for the mole ratio of (i) to (ii) includes about 1:1 to 1:3.
In another exemplary embodiment, a reaction product is obtained by reacting together i) an acylated alkylacrylate copolymer having a weight average molecular weight ranging from about 5,000 to about 500,000; ii) a polyalkylene succinic acid or anhydride; and iii) a compound selected from (a) a polyamine; (b) a polyol; and (c) an aminoalcohol to provide a functionalized polyalkylacrylate copolymer, wherein a mole ratio of (i) to (ii) ranges from about 1:10 to about 5:1.
Among other advantages, the copolymer reaction products made according to the disclosed embodiments may have good dispersancy, thickening efficiency, low temperature properties, soot handling properties, fuel economy, and/or antioxidancy properties, and are substantially devoid of gels. The reaction products have improved low temperature properties and are useful in crankcase formulation packages, amongst other applications. Some necessary components within traditional lubricating oil, such as friction modifiers and grade of base oil, have generally tended to improve a formulation's low temperature properties. However, other components such as certain polymers, such as polyisobutylene-based dispersants, have been observed to negatively impact an oil formulation's low temperature properties. Although the use of a higher grade of base oil (e.g., Group II+ or Group III) in a formulation can improve an oil's fuel economy, these higher grades of base oil require more complex refinery processing, and thus add more cost to the resulting oil formulation. It has been discovered that the reaction product additives having improved low temperature properties according to disclosed embodiments may reduce or eliminate the need to use expensive base oils in lubricant formulations.
The reaction products described herein may also be used in engine oil applications to improve or boost dispersancy, oxidation, high temperature high shear (HTHS)/fuel economy, and low temperature viscometrics (e.g., cold cranking simulator (CCS) and mini-rotary viscometer (MRV) properties) in conjunction with conventional dispersants and at a lower olefin copolymer (OCP) loading in the finished oil. Particularly, the disclosed reaction products may exhibit outstanding low temperature properties in lubricating oils for applications such as crankcase lubricants and automatic transmission fluids. The reaction products may also exhibit excellent low temperature performance in a wide variety of base oils. Improved fuel economy, such as measured via Sequence VIB engine testing, may also be obtained with oils containing the reaction products embodied herein.
The reaction products may also be precipitation- or sedimentation-resistant, and may not cause or encourage such formations in finished fluids incorporating the reaction products. The reaction products may be further characterized as polymer bound antioxidants having a potential to enhance the oxidative stability and dispersancy of lubricants which may be limited by the thermal and oxidative stability of conventional lower molecular weight antioxidants.